My best advice to you is , if you have any doubts, move on. You will have this pup for a very long time. You should love everything about it.

I get liking a color, I have no issue with that being a priority, but it should never trump personality.

Your son is likely to have friends over, kids are rowdy, you want a dog that wants to interact. I would either wait to see if the youngest female is a better match temperament wise, check out the male pups, or find a different breeder.

Don't feel you have to buy from this breeder. You don't owe her anything. You do owe your family the right dog, even if that means paying more in the beginning. Worrying about cost now is pointless. Pups are expensive. Trying to save money up front is more likely bite you on the back end later.